If this does not solve the issue and you continue to receive an error along the lines:

"The file couldn’t be opened because it isn’t in the correct format. The file might be corrupted, truncated, or in an unexpected format"

Then this may indicate a corrupt database. To fix this:

Launch BusyCal / BusyContacts while holding down the option key (⌥) to display the Startup Options dialog, then select Reset BusyCal / BusyContacts and click Continue. Resetting BusyCal will delete your database, and quit. All of your data will be preserved on iCloud, Google and/or Exchange. For users with local calendars / address books, automatic backups will have already been created.

Launch the app and go through the setup assistant.

If the app does not automatically connect to your iCloud, Google or Exchange accounts, you may connect to them manually in BusyCal > Preferences > Accounts.

Note: If syncing with iCloud, you will have to re-enter your iCloud app-specific password for BusyCal. If you have forgotten your iCloud app-specific password, you can create a new one and use the new app-specific password instead. You can learn more about creating an app-specific password here: